JP2003171419A - Gas barrier resin composition and gas barrier film formed from the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas barrier film which holds a gas barrier property even under a high humidity, can be produced in excellent productivity, and is hardly discolored. <P>SOLUTION: This gas barrier resin composition is characterized by reacting a polycarboxylic acid-based polymer with a cross-linking agent having two to four functional groups reacting with the carboxy groups and a divalent or more metal ion to form cross-linked sites due to the cross-linking agent and cross-linked sites due to the divalent or more metal ion on the polycarboxylic acid-based polymer, and having a polycarboxylic acid-based polymer/cross-linking agent weight ratio of 99.9/0.1 to 65/35. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gas barrier resin composition and a gas barrier film using the same.

[0002]

2. Description of the Related Art In the field of packaging foods and medicines, packaging materials having excellent gas barrier properties such as oxygen gas barrier properties are used for the purpose of preventing quality deterioration of contents. As such a gas barrier film, a film in which polyvinylidene chloride is laminated, a film using a polyvinyl alcohol resin, and the like are known. In particular, a film obtained by laminating the above polyvinylidene chloride is widely used for food packaging.

[0003]

However, the film in which the above polyvinylidene chloride is laminated tends to be refrained from use due to recent environmental problems such as dioxin.

The film using the polyvinyl alcohol resin has a problem that the gas barrier property under high humidity is deteriorated because the polyvinyl alcohol resin contains a hydroxyl group. On the other hand, for example, Japanese Patent Laid-Open No. 10-2
Japanese Patent No. 37180 discloses a film coated with a resin obtained by ester-crosslinking and ion-crosslinking a polyalcohol-based resin and a partially neutralized product of polyacrylic acid or polymethacrylic acid. Although this film has improved gas barrier properties under high humidity, it requires high-temperature and long-time reaction to carry out the esterification reaction, and also has a problem of productivity. Further, there is a problem that the obtained coat layer is colored.

Further, Japanese Patent Laid-Open No. 2001-310425 discloses a gas barrier film composed of polyacrylic acid and a cross-linking agent component, but the gas barrier property of the obtained film is not always sufficient. There is.

[0006] Therefore, an object of the present invention is to provide a gas barrier film which retains gas barrier properties even under high humidity and is excellent in productivity and in which coloring is less likely to occur.

[0007]

According to the present invention, a polycarboxylic acid-based polymer is reacted with a crosslinking agent having 2 to 4 functional groups capable of reacting with a carboxyl group and a divalent or higher valent metal ion. The polycarboxylic acid-based polymer is formed with a cross-linking site by a cross-linking agent and a cross-linking site by the above-mentioned divalent or more metal ion, and the weight ratio of the polycarboxylic acid-based polymer to the cross-linking agent is 99.9 / 0.1. 65
By setting the ratio to / 35, the above problem is solved.

Since the cross-linking site is provided in the polycarboxylic acid type polymer by the specific cross-linking agent, the hot water resistance of the obtained resin composition can be improved. Further, since the polycarboxylic acid-based polymer is provided with a cross-linking site by a metal ion having a valence of 2 or more, the hot water resistance of the obtained resin composition can be further improved, and the gas barrier property under high humidity can be improved. it can.

Furthermore, since the amount of the specific cross-linking agent used is within the predetermined range, the gas barrier property under high humidity can be enhanced without impairing the appearance of the resin composition finally obtained. Furthermore, by using a specific cross-linking agent, the reaction conditions can be milder than those of the esterification reaction, and the productivity can be improved. In addition, since it is crosslinked with a specific crosslinker and a metal ion having a valence of 2 or more
It is possible to further improve the hot water resistance and the gas barrier property as well as the productivity.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The gas barrier resin composition according to the present invention is obtained by reacting a polycarboxylic acid-based polymer with a cross-linking agent and a divalent or higher valent metal ion, whereby the polycarboxylic acid-based polymer is cross-linked with the cross-linking agent and the divalent It is a composition in which a crosslinked site is formed by the above metal ions.

As the above polycarboxylic acid type polymer,
Polyacrylic acid, polymethacrylic acid, polymaleic acid,
A homopolymer or copolymer of a monomer having a carboxyl group such as polyitaconic acid or acrylic acid-methacrylic acid copolymer. Further, partially neutralized products of homopolymers or copolymers of monomers having a carboxyl group such as the above polyacrylic acid, polymethacrylic acid, acrylic acid-methacrylic acid copolymer and the like can be mentioned. Among these, polyacrylic acid, polymethacrylic acid and neutralized products thereof are preferable.

As the alkaline substance for partially neutralizing the homopolymer or copolymer of the above-mentioned monomer having a carboxyl group, sodium hydroxide, potassium hydroxide,
Examples thereof include metal hydroxide salts such as lithium hydroxide and ammonia. The partially neutralized product can be obtained by adding the metal hydroxide salt to an aqueous solution of a polycarboxylic acid polymer and reacting them.

The degree of neutralization of the partially neutralized product is not particularly limited, but is preferably 2 to 30% and more preferably 5 to 20% in terms of molar ratio to the carboxyl group. If it is less than 2%, the reactivity with the cross-linking agent is lowered, and the productivity tends to be lowered. On the other hand, if it is more than 30%, the number of reaction points with the cross-linking agent itself decreases, and the gas barrier property of the final resin composition tends to deteriorate.

The weight average molecular weight of the above polycarboxylic acid type polymer is not particularly limited, but is 2000 to 500,0.
00 is preferable, and 20,000 to 400,000 is more preferable. If it is less than 2000, the gas barrier property of the finally obtained resin composition tends to deteriorate. on the other hand,
When it is more than 500,000, the viscosity of the aqueous solution becomes too high, which is not preferable.

The cross-linking agent refers to a compound having 2 to 4 functional groups that easily react with a carboxyl group, and refers to a compound that forms a cross-linking site in the polycarboxylic acid polymer. Since there are two or more functional groups that react with a carboxyl group, it is possible to cause a crosslinking reaction with respect to the polymer chains of a plurality of polycarboxylic acid-based polymers. Further, since the number of functional groups that react with the carboxyl group is 4 or less, the molecular weight of the crosslinking agent itself is not so high, and the reaction temperature during the crosslinking reaction can be further lowered.

Examples of the cross-linking agent include isocyanate compounds having 2 to 4 functional groups, epoxy compounds, urea compounds, amine compounds, carbodiimide compounds and amino acid compounds. Among these, isocyanate compounds, epoxy compounds, urea compounds and amine compounds are preferable. At least one of these may be used, and only one may be used or two or more may be used in combination.

Specific examples of the above-mentioned isocyanate compound include blocked isocyanate compounds (for example, trade name Elastron BN series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.),
Tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, 4,4'-methylenebiscyclohexyl diisocyanate, isophorone diisocyanate and the like are mentioned, and blocked isocyanate compounds are preferably used.

Specific examples of the above epoxy compounds include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, tetraethylene glycol diglycidyl ether, nonaethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and diethylene glycol diglycidyl ether. Propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, 1,6
Hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, diglycidyl ethers such as glycerol diglycidyl ether, triglycidyl ethers such as glycerol triglycidyl ether, and tetraglycidyl ethers such as pentaerythritol tetraglycidyl ether. Ethylene glycol diglycidyl ether is preferably used.

A specific example of the above-mentioned urea compound is urea, which is preferably used. Specific examples of the amine compound include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, propylenediamine, 1,7-diaminoheptene, 1,8-diaminooctane and 1,9-diaminononane. , 1,10-diaminodecane, o-, m-, p-phenylenediamine, tolylenediamine, diphenylene, diamines such as 4,4-diaminodiphenyl ether, triamines such as melamine and paraleucoaniline, tetraaminobiphenyl, etc. Tetraamines and the like.

Specific examples of the carbodiimide compound include cyanamide and dicyclohexylcarbodiimide. Moreover, lysine, arginine, etc. are mentioned as a specific example of the said amino acid compound.

In addition to the above-mentioned cross-linking agent, a catalyst or the like can be appropriately added in order to enhance the reactivity between the above-mentioned polycarboxylic acid type polymer and the cross-linking agent.

The weight ratio of the polycarboxylic acid type polymer to the crosslinking agent is as follows: polycarboxylic acid type polymer / crosslinking agent = 9
9.9 / 0.1-65 / 35 is good, 99 / 1-80 /
20 is preferable. If the cross-linking agent is less than 0.1% by weight,
The water resistance of the resin composition becomes low. On the other hand, if it is higher than 30% by weight, the gas barrier property of the final product tends to be deteriorated.

The above-mentioned divalent or higher valent metal ions are those which form an ionic bond with the carboxyl group of the aforementioned polycarboxylic acid type polymer and have divalent or higher valent cations. Since this metal ion has a positive ion with a valence of 2 or more,
An ionic bond can be formed with one or more carboxyl groups, and a crosslinking site can be formed in the carboxylic acid-based polymer.

The divalent or higher valent metal ions include magnesium ions, calcium ions, barium ions,
Examples thereof include zinc ion, copper ion, cobalt ion, nickel ion, aluminum ion and iron ion. Among these, magnesium ion, calcium ion, and barium ion are preferably used. At least one of these may be used, and only one may be used or two or more may be used in combination.

The divalent metal ion is preferably used in the state of an alkaline aqueous solution. When used in this state, the exchange reaction between the metal ion and the counter ion of the carboxyl group proceeds, the ionic cross-linking site is formed, and the composition is stabilized. Examples of the alkaline aqueous solution include aqueous solutions of metal salt hydroxides and the like, and alcoholic aqueous solutions containing alcohol and the like may be used. Specifically, a magnesium hydroxide aqueous solution, a calcium hydroxide aqueous solution, a barium hydroxide aqueous solution and the like are preferably used.

The above gas-barrier resin composition can be produced by reacting a polycarboxylic acid type polymer with a crosslinking agent and then reacting it with an alkaline aqueous solution of a divalent or higher valent metal ion. The reaction condition in the reaction with the above-mentioned cross-linking agent is 100-
At 230 ° C., 1 second to 60 minutes is preferable.

The reaction with the divalent or higher valent metal ion is carried out by applying an aqueous solution of the divalent or higher valent metal ion to the cross-linking reaction product of the polycarboxylic acid polymer and the cross-linking agent, or by the cross-linking product. Is immersed in an aqueous solution of the above-mentioned divalent or higher valent metal ions. The reaction conditions at this time are preferably 10 to 120 ° C. and 1 second to 60 minutes.

The above gas barrier resin composition is molded by
It is preferable to carry out up to the stage where the crosslinking agent is mixed with the polycarboxylic acid polymer. When heated to cause a crosslinking reaction between the polycarboxylic acid-based polymer and the crosslinking agent to form a crosslinking site,
This is because molding is often difficult.

For preparing the mixed solution of the polycarboxylic acid type polymer and the crosslinking agent, a method of dissolving each component in water, a method of mixing an aqueous solution of each component, or the like can be applied. In addition to water, a solvent such as alcohol or a mixed solvent such as water / alcohol may be used.

As a molding method, the above mixed solution is extruded from a T-die or the like and heated to form a film into a film, or the mixed solution is cast onto a glass plate, a plastic film or the like. A method of forming into a film, a method of producing a laminate in which a film is laminated on a substrate by applying the mixture on at least one surface of a substrate and heating the mixture, and a raw material resin for the substrate. A method for producing a laminate in which a film is laminated on a substrate by heating while coextruding, extruding from the above T die or the like, and joining the film obtained by heating to the substrate to form the film on the substrate. The method of manufacturing the laminated body laminated | stacked on.

The obtained film or laminate is coated with the aqueous solution of divalent or higher valent metal ions on the mixed solution coating layer side, or the film or laminate is dipped in the aqueous solution of divalent or higher valent metal ions. And reacting to form a cross-linking site by a metal ion having a valence of 2 or more, and a film or laminate having a gas barrier property is obtained.

The base material is not particularly limited as long as the gas barrier property is imparted to the entire laminate by laminating the gas barrier resin composition, and examples thereof include polyester resins and polyamide resins. resin,
Examples thereof include synthetic resins such as polyolefin resins and cellulosic materials such as cellophane and paper. Further, as the shape of the base material, any shape such as a film shape, a sheet shape, and a molded body such as various containers can be adopted.

In the present invention, water-swellable inorganic tabular grains such as vermiculite and montmorillonite can be added to the solution containing the above polycarboxylic acid type polymer and the crosslinking agent. By molding this, the performance of the final gas barrier composition can be further enhanced.

[0034]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below. First, the substances used are shown below. -Polyacrylic acid: manufactured by Wako Pure Chemical Industries, Ltd., first-class reagent, weight average molecular weight of about 250,000-Isocyanate compound: Elastron BN-11 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) (referred to as "isocyanate" in Table 1) Epoxy compound: ethylene glycol diglycidyl ether (manufactured by Kishida Chemical Co., Ltd .; reagent) (in Table 1,
Abbreviated as "epoxy".・ Urea compound: Urea (Katayama Chemical Co., Ltd .; Reagent) ・ PVA: Polyvinyl alcohol (Wako Pure Chemical Industries, Ltd.)
Made; polyvinyl alcohol 1000, completely saponified type)
(In Table 1, abbreviated as "PVA".) Starch: Soluble starch (Kishida Chemical Co., Ltd .; reagent)

[Preparation of partially neutralized polyacrylic acid] Polyacrylic acid was dissolved in ion-exchanged water so that the solid content was 3% by weight. Add 10 mol% sodium hydroxide to the carboxyl group of polyacrylic acid, and neutralize to 1
0% partially neutralized polyacrylic acid (hereinafter referred to as "PAA-N
Abbreviated as a ". ) Was prepared.

(Examples 1 to 12) A crosslinking agent was mixed with the above solid content of PAA-Na so as to have a compounding ratio shown in Table 1. Stretched polyester film (E5100, manufactured by Toyobo Co., Ltd., thickness: 12 μm)
It was applied to the corona-treated surface of No. 2 with a Mayer bar so that the thickness of the coating film after drying was 1 μm. After drying at 100 ° C. for 2 minutes, the heat treatment was performed at the heat treatment temperature shown in Table 1 for 15 minutes in a hot air dryer. Then, the metal ion hydroxide shown in Table 1 (manufactured by Wako Pure Chemical Industries, Ltd .; reagent) was dipped in a 0.2% by weight aqueous solution for 30 minutes, washed with water, dried at 100 ° C. for 2 minutes, and laminated. A body film was obtained. Using the obtained laminate film, according to the following method, the oxygen permeability,
The hot water resistance and appearance were measured or judged.

[Oxygen permeability] Oxygen permeability tester (Mode
RN Control; OX-TRAN2 / 2
0), the target film is 23 ℃, relative humidity 80%
The oxygen permeability in the atmosphere was measured. Since the oxygen permeability changes depending on the thickness of the film, the thickness of the gas barrier resin composition layer, etc., the oxygen permeability per 1 μm of the gas barrier resin composition layer was calculated according to the following formula. 1 / P _total = 1 / P _sample + 1 / P _{base In the} above formula, P _total is the measurement result, P _sample is the oxygen permeability of the gas barrier resin composition layer, and P _base is the oxygen permeability of the base film. Show.

[Hot Water Resistance] The target film was immersed in warm water of 80 ° C. for 30 minutes, and the weight reduction of the gas barrier resin composition layer was measured. The results were evaluated according to the following criteria. ◯: Weight remaining ratio is 100% Δ: Weight remaining ratio is 50% or more and less than 100% ×: Weight remaining ratio is less than 50%

[Appearance] The appearance of the target film was evaluated according to the following criteria. ◯: No difference compared to the base film alone x: Colored xx: Gas barrier resin composition layer peels off / swells

Comparative Examples 1 to 5 Laminate films were obtained in the same manner as in Example 2 except that PVA or starch was used as the crosslinking agent and the compounding ratios shown in Table 1 were used. Using the obtained laminate film, the oxygen permeability, the hot water resistance, and the appearance were measured or judged according to the methods described above.

(Comparative Example 6) Example 2 except that the compounding ratio of the partially neutralized polyacrylic acid and the crosslinking agent was 60/40.
A laminate film was obtained in the same manner as. Using the obtained laminate film, the oxygen permeability, the hot water resistance, and the appearance were measured or judged according to the methods described above.

(Comparative Example 7) The heat treatment temperature was set to 200 ° C,
A laminate film was obtained in the same manner as in Example 4, except that the metal ion hydroxide was not used to form the crosslinked site.
Using the obtained laminate film, the oxygen permeability, the hot water resistance, and the appearance were measured or judged according to the methods described above.

Comparative Example 8 A laminate film was obtained in the same manner as in Example 2 except that no crosslinking agent was used and no heat treatment was performed. Using the obtained laminate film, the oxygen permeability, the hot water resistance, and the appearance were measured or judged according to the methods described above.

[0044]

[Table 1]

[0045]

EFFECTS OF THE INVENTION The gas barrier resin composition according to the present invention and the film or laminate obtained therefrom have a crosslinking site in the polycarboxylic acid-based polymer by a crosslinking agent. The hot water resistance can be improved.

Since the polycarboxylic acid type polymer is provided with a cross-linking site by a metal ion having a valence of 2 or more, the hot water resistance can be further improved and the gas barrier property under high humidity can be improved.

Furthermore, since the amount of the cross-linking agent used is within the predetermined range, the gas barrier property under high humidity can be enhanced without impairing the appearance of the resin composition finally obtained.

Furthermore, by using a specific cross-linking agent, the reaction conditions can be milder than those of the esterification reaction, and the productivity can be improved. Further, since the specific cross-linking agent is cross-linked with a metal ion having a valence of 2 or more, the productivity can be improved and the hot water resistance and the gas barrier property can be further improved.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Susumu Sakata             4-1-1, Daikai 4-chome, Fukushima-ku, Osaka             Go Central Research Institute (72) Inventor Masao Fujita             4-1-1, Daikai 4-chome, Fukushima-ku, Osaka             Go Central Research Institute F-term (reference) 4F071 AA08 AA29 AA32 AA36 AB18                       AC12 AC19 AE02 AF08 AH04                       BA02 BB07 BC01                 4F100 AH03B AH08B AJ06A AK03A                       AK25B AK41A AK46A AT00A                       BA02 CA02B GB15 JD02                       JD02B JJ03                 4J100 AJ02P AJ08P AJ09P HA53                       HB39 HC39 HC43 HC47 HC51                       HC54 HC57 JA59

Claims (11)

[Claims] 1. A polycarboxylic acid-based polymer, a cross-linking agent having 2 to 4 functional groups which react with a carboxyl group, and 2
The polycarboxylic acid-based polymer and the cross-linking agent are formed by reacting the polycarboxylic acid-based polymer with a cross-linking agent and a cross-linking site by the divalent or higher-valent metal ion by reacting with a metal ion having a valency or more. And a gas barrier resin composition having a weight ratio of 99.9 / 0.1 to 65/35. 2. An isocyanate compound, an epoxy compound, a urea compound, wherein the cross-linking agent has 2 to 4 functional groups,
The gas barrier resin composition according to claim 1, which is at least one selected from amine compounds, carbodiimide compounds, and amino acid compounds. 3. The gas barrier resin composition according to claim 1, wherein the divalent or higher valent metal ion is at least one selected from magnesium ion, calcium ion and barium ion. 4. The polycarboxylic acid-based polymer is at least one selected from polyacrylic acid, polymethacrylic acid, polyacrylic acid or a partially neutralized product of polymethacrylic acid.
The gas barrier resin composition according to claim 1 or 2, which is a seed. 5. A gas barrier film formed from the gas barrier resin composition according to claim 1. 6. A gas barrier film in which the gas barrier resin composition according to claim 1 is applied to at least one surface of a substrate. 7. The gas barrier film according to claim 6, wherein the substrate is at least one selected from polyester resins, polyamide resins, and polyolefin resins. 8. The gas barrier film according to claim 6, wherein the base material is made of a cellulose material. 9. A gas barrier laminate having the gas barrier film according to claim 5 laminated thereon. 10. A method for producing a gas barrier resin composition, which comprises reacting a polycarboxylic acid-based polymer with a crosslinking agent and then reacting with an alkaline aqueous solution of a divalent or higher valent metal ion. 11. A method for producing a gas barrier film, which comprises reacting a polycarboxylic acid-based polymer with a crosslinking agent, forming the film into a film, and then reacting it with an alkaline aqueous solution of a divalent or higher valent metal ion.